VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics


Go Back   VAF Forums > Model Specific > RV-8/8A
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 01-20-2020, 11:49 AM
scsmith scsmith is offline
 
Join Date: Jan 2008
Location: Ashland, OR
Posts: 2,546
Default RV-8 fastback canopy question

I am thinking ahead to a repeat offense. Premeditation, if you will.

I have a question about the shape and fit of the canopy on a fastback.

When I look at my standard canopy and look at the cross section at the station where the fastback canopy frame/skirt would attach at the back seat bulkhead, the standard canopy has, well to use a naval architecture term, tumblehome. This means that the canopy contour is wider up away from the bottom edge of the skirt, and is getting narrower along the bottom edge. Said another way, the canopy bulges out beyond the skirt.

The Showplanes website says their kit uses a standard canopy, yet the shape of the bulkhead at the rear seat back does not fit this tumblehome shape. It is widest at the bottom, and has a normal oval shape.

So, it would seem that fitting a standard canopy to the fastback skirt and fuselage shape would require flexing the canopy to fit that shape. This concerns me because it puts a bunch of pre-stress into the canopy.

When I fit my standard canopy, I took care to shape the canopy frame so that it fits the canopy in its completely relaxed state - no built-in stresses. That plus Sikaflex and I think/hope it will never crack. I would be really worried that forcing the canopy into a different shape would be asking for trouble.

Thoughts? DanH? Scard? Scott Hersha? Others?
__________________
Steve Smith
Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet"
Hobbs 625
LS6-15/18W sailplane SOLD
bought my old LS6-A back!!
VAF donation Jan 2020
Reply With Quote
  #2  
Old 01-20-2020, 12:02 PM
rvbuilder2002's Avatar
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,003
Default

Quote:
Originally Posted by scsmith View Post
Thoughts? DanH? Scard? Scott Hersha? Others?
I am none of those people and I haven't done a show planes canopy installation, I am familiar with what the canopy does once it has been cut.

When the rear portion that will not be used is removed they canopy gets very flexible in that area and should easily adapt to the different shape without inducing any undo stress.

You may remember this with your current RV-8, when the fwd windscreen portion was removed from the main canopy.
__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
Reply With Quote
  #3  
Old 01-20-2020, 01:42 PM
sjhurlbut sjhurlbut is offline
 
Join Date: Jan 2005
Posts: 832
Default canopy

Canopy fits perfectly on the fastback mod. While mine has a tint to it you do not need to force it into place.

The canopy is cut a bit shorter (from bottom) than you would with a standard steel frame installation which may cause the bulging you mention.

Check out the youtube channel to see - maybe I'll get more info (video) on it if you wish.

https://www.youtube.com/channel/UCGQ..._as=subscriber
__________________
Visit and subscribe to Stu's Aircraft Factory on

https://www.youtube.com/channel/UCGQ..._as=subscriber

Steve "Stu"
Cold Lake, Alberta
7A #70015 - C-FZQX - built - sold
7A #71629 - C-FSIS - built - sold across Atlantic
7 #70215 - C-GOJU - flying - sold
7 #70703 - C-GMIY - flying - sold
6 #60119 - C-FHBZ - built - Airventure 2016 Bronze Lindy - sold
8 #82842 - C-FSBG - Fastback - built - sold
4 #2723 - building
Reply With Quote
  #4  
Old 01-20-2020, 01:58 PM
scard's Avatar
scard scard is offline
 
Join Date: Jun 2005
Location: Cedar Park, TX
Posts: 3,143
Default

There is no "pre-stress" at all in my canopy and it doesn't "bulge" anywhere. Mine is a Todd's canopy, but I suspect is quite similar in shape to the standard.
__________________
Scott Card
CQ Headset by Card Machine Works
CMW E-Lift
RV-9A N4822C flying 2200+hrs. / Cedar Park, TX
RV8 Building - fuselage / showplanes canopy (Done!)
Reply With Quote
  #5  
Old 01-20-2020, 03:55 PM
DanH's Avatar
DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
Posts: 9,443
Default

I'm using a standard Vans canopy, circa 2006. It has been glued into that glass frame 10 years or more, no issues.

As Stu suggested, I think a lot of the tumblehome gets cut off. That said, I cut mine tall.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
Reply With Quote
  #6  
Old 01-20-2020, 09:09 PM
scsmith scsmith is offline
 
Join Date: Jan 2008
Location: Ashland, OR
Posts: 2,546
Default

So, is the bottom edge of the exposed canopy higher than the stock slider canopy?
__________________
Steve Smith
Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet"
Hobbs 625
LS6-15/18W sailplane SOLD
bought my old LS6-A back!!
VAF donation Jan 2020
Reply With Quote
  #7  
Old 01-21-2020, 05:07 AM
Daida's Avatar
Daida Daida is offline
 
Join Date: May 2005
Location: Hannover, Germany
Posts: 118
Default

As far as i remember, the canopy (standard Van?s) is thermoformed like a bath-tub and ends with a 90 degree angle to the edge (which is supposed to be cut of anyway).
Therefore, to create this (standard, according to plans -8 slider canopy) ?double bubble? / F-16 like / bulged canopy, the lower outer canopy edges are pushed inwards to meet the form of the canopy-frame. Thus creating a pre-stress on the canopy.
This doesn?t cause too many problems as over a thousand RV-8?s are out there flying and only once in a while you see posts about cracks.

I would figure that, if the showplanes/fastback canopy lower end is vertical (not bulged in), that there is no pre-stress on the canopy whatsoever.
__________________
RV-8 QB Germany
ECi XIO-360
Dynon SV

Flying since 11th July 2020
Reply With Quote
  #8  
Old 01-21-2020, 05:53 AM
Larry DeCamp's Avatar
Larry DeCamp Larry DeCamp is offline
 
Join Date: Apr 2010
Location: Clinton, Indiana
Posts: 989
Default Tumblehome reshape option

Steve,
Jeff at airplane plastic will stress relieve the plex to conform to your rear frame or bulkhead shape. Yon need a wooden form and a way to clamp the plex against it. He heats to about 180F and the plastic conforms when cool.
Just one option... Larry
__________________
Larry DeCamp
RV-3B flying w/7:1 0320 / carb / Pmags / Catto 3b / digital steam
RV-4 fastback w/ Superior roller 360/AFP/G3X/CPI/Catto3b
Clinton, IN
Reply With Quote
  #9  
Old 01-21-2020, 06:25 AM
DanH's Avatar
DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
Posts: 9,443
Default

Quote:
Originally Posted by scsmith View Post
So, is the bottom edge of the exposed canopy higher than the stock slider canopy?
Now that you ask, I don't think so.

Nothing handy to compare.

I assume the tumblehome observation comes from your existing slider? None of my photos show any at the rear of this canopy.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
Reply With Quote
  #10  
Old 01-21-2020, 07:06 AM
Scott Hersha Scott Hersha is offline
 
Join Date: Jan 2005
Location: Cincinnati, OH
Posts: 1,544
Default

Steve,
When I fit my canopy on the Showplanes frame, I slid it forward to get the shape I wanted. I was looking for a little more slope at the front and that resulted in a little less slope at the back. As others have said, when you trim off the bottom edge and then trim the back portion where you want it, the canopy becomes quite flexible. If you do what I did, be mindful of canopy height. If you reposition it too far forward (before trimming) you will loose some headroom if you go too far. The standard Vans canopy is quite a bit longer than what you will need so there is room to adjust it where you want it. Mine was glued on in 2007 with a thickened structural epoxy from the Gougeon Brothers (West System) called ProSet. It has a fairly long pot life, giving you plenty of time to work with it when fitting before it sets up. It is compatible with all West System epoxies and will wet out cloth also if needed while doing the install. Spaceship 1 was glued together with this stuff...
__________________
SH
RV6/2001 built/sold 2005
RV8 Fastback/2008 built/sold 2015
RV4/bought 2016/sold/2017
RV8/2018 built/Sold(sadly)
RV4/bought 2019 Flying
Cincinnati, OH/KHAO
JAN2020
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 03:32 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.